In the wood processing industry for example, wood grading and wood classification is an important step to sort out a variety of wood grades in accordance with specific applications.
Traditionally, grading of planed lumbers is done by a qualified operator. The operator examines and segregates the wood pieces according to a numeric grade such as grade 1, grade 2, and grade 3 following predetermined standards. This evaluation must be done very rapidly, generally at a rate of sixty pieces per minute per operator, according to several criteria and in adherence to stringent rules. Grading allows selecting and dispatching wood pieces according to the specific applications and to a client's needs, thereby allowing rationalizing the use of wood in a cost-effective way.
Typically, classification is done according to norms generated by national commissions with the purpose of obtaining uniform characteristics and quality throughout plants manufacturing a given type of wood. The current norms allow a maximum variation between graders of 5% of “under-classification”.
Obviously, the operators work under tremendous pressure. Moreover, evaluation standards used by the operators are so strict that they result in “over-quality”, meaning that approximately 15% of the wood pieces are over-classified, i.e. graded in an inferior grade, which in turn results in reduced profits. Furthermore, since automation efforts have increased the manufacturing rates up to 200 wood pieces per minute, classification by operators at a maximum rate of 60 pieces per minute constitutes a major bottleneck.
A number of technologies have been developed to automate the classification work. However, few have been successful in increasing the rate of classification and allowing reducing human intervention while maintaining the desired quality.
Indeed, a number of attempts have been made to simplify and accelerate wood classification. Since evaluation of an object requires that a peripheral surface thereof is evaluated, it has been contemplated positioning cameras above and under a conveyor carrying the wood pieces for example, but a recurrent problem is the accumulation of debris on lower cameras. In U.S. Pat. No. 5,412,220 issued to Moore in 1995, this problem is addressed by adding to the conveyor a mechanism to rotate each wood piece in such a way that all four longitudinal faces thereof can be exposed to a camera.
In spite of such developments, there is still a need for a system and a method for evaluating and classifying objects such as lumber planks or timbers and wood pieces for example, for subsequent treatment, which allow quality and speed at a reasonable price and with an increased performance.